Pivoted type moving coil galvanometer- Working principle,Construction and working.

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MOVING COIL
GALVANOMETER.
RIYAS K

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Moving Coil galvanometer
A moving coil
galvanometer is
a device to
detect or
measure
electric current
in a circuit.

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Working principle.
●
A current carrying
coil experiences a
torque in a uniform
magnetic field which
deflects the coil in
the field.
●
For a galvanometer,
deflection is
proportional to the
current.

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Construction and Working
1.Horse Shoe Magnet- To provide a
uniform radial magnetic field
powerful cylindrical magnet is used.
2.Coil- coil consists of large number
of copper wires wound over a
frame.
3.Spring- A light spring is provided
at the centre and develops a
restoring torque while the coil
deflects.
4.Pointer- The pointer moves along
the arc of a graduated scale.

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The deflecting Torque on the coil
due to the current flow...
τ=i N A B
The restoring torque developed in
spring as the coil deflects...
τ=C θ C-couple per unit twist.
θ-angle of twist.

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i N A B=C θ
i=
Cθ
N A B
i=K θ K =
C
N A B
i α θ
When the restoring torque balances deflecting
torque, the coil rests in the deflected position.
Current through the coil proportional to the deflection.

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Current Sensitivity.
Deflection produced for unit current passing
through the coil.
Si= θ
i
Si=
N A B
C
i N A B=C θ
Current sensitivity can be
increased by
●
Increasing N
●
Increasing A
●
Increasing B – best method
●
Decreasing C

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Voltage Sensitivity.
Deflection produced for unit Voltage applied
between the terminals of the coil.
Sv= θ
V
i N A B=C θ
Sv=
N A B
C R
Voltage sensitivity can be
increased by increasing.
●
Increasing N
●
Increasing A
●
Increasing B- best method
●
Decreasing C and R

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THANK YOU...